Assessing a herd for hyperkeratosis

Recently, a farmer called me because a consultant had recommended changing pulsation settings in her parlor. This consultant thought that fewer of their cows might suffer from teat-end hyperkeratosis if the settings were changed.

When I asked the farmer if her herd had a high incidence of hyperkeratosis, she said, “I don’t know.”

“Well, if that is the case, it seems the first thing we should do to answer the question is score teats on at least 80 cows on your dairy,” I said.

She agreed, and I scored 320 teats on 80 high-producing cows the next day. 16% of cows had at least one teat that scored rough or very rough, with 10% of the 320 teats scoring rough or very rough.

National Mastitis Council standards say that when either 20% of cows or 20% of teats score rough or very rough, there is likely to be a problem. However, I seldom find more than 5% of teats and 8% of cows with rough or very rough teat ends on high-producing farms, so I felt that hyperkeratosis was somewhat of a problem on this dairy.

My client’s farm is an elite dairy: extremely high production, beautiful cows, great animal health, etc., so the prevalence of rough teat ends stuck out as too high for this farm, and the farmer agreed. Plus, there were more teats that scored very rough, and more of those cows had long, pointy teats than I expected.

Hyperkeratosis can be problematic because rough teat ends are more likely to lead to mastitis, and rough teat ends may increase milking time. Long, pointy teats may be genetic, but they also may develop from milking with improper design or operation of milking systems.

Hyperkeratosis is usually caused by excessive time in low milk flow. Teat-end vacuum level is inversely related to milk flow, so low flows result in higher teat-end vacuum, and higher teat-end vacuum results in hyperkeratosis.

In a perfect milking system, line vacuum and teat-end vacuum would be the same throughout the entire milking period. While this is theoretically possible in a low line system, it does not happen in high-producing cows at peak milk flow, because high milk flows reduce vacuum. Thus, line vacuum needs to be adjusted higher to achieve adequate peak flow vacuum.

Any restriction between the teat end and the line means that line vacuum will need to be raised more to achieve adequate claw vacuum, which means more potential for teat exposure to high vacuum levels. There are two periods during milking where low flow, and thus high teat end vacuum, may be present: at the beginning and at the end. High vacuum may occur at the beginning of milking if udder stimulation or prep-lag time to attachment are not correct. High vacuum happens at the end of milking when milk flow declines and units are not promptly removed. Neither of these appeared to be a problem on this farm. However, line vacuum measured surprisingly high, even though the farm did have milk meters.

The farm had a type of vacuum shut-off valves that, according to noted milking equipment expert Dr. David Reid, can cause significant restriction to milk flow. Indeed, I was able to measure up to nearly 1 inch of vacuum difference between the inlet and the outlet of the shutoff valve. This means that the teat end vacuum is nearly 1 inch higher at the beginning and end of milking than it would need to be if not for the design of this valve. Besides causing hyperkeratosis, significant differences between line vacuum and claw vacuum usually result in lower peak flow claw vacuum on the highest-producing cows. This results in longer milking unit on time, which can also cause more hyperkeratosis and potentially the harvest of less milk at every milking on the farm’s very best cows. So, anything that causes a restriction, such as this shut-off valve, for example, could result in more mastitis, longer milking times and less milk harvested. All of a sudden, those valves look very expensive.

Milking systems should be designed and maintained to eliminate unnecessary restrictions to air and milk flow. High line systems need to have higher line vacuum to move milk, but if udder stimulation is good, prep-lag times are correct and units are taken off promptly when milk flow declines, adequate claw vacuum and rapid milk out can be achieved without causing significant hyperkeratosis, even in high line systems. Milking cows correctly, safely and rapidly are keys to harvesting more milk and maintaining great udder health.

Jim Bennett is one of four dairy veterinarians at Northern Valley Dairy Production Medicine Center in Plainview, Minnesota. He consults on dairy farms in other states. He and his wife, Pam, have four children. Jim can be reached at [email protected].